For example, in a semiconductor chip manufacturing process, there has been widely used a pressure sensor configured to include a capacitance detecting portion in a capacitance chamber partially formed of a diaphragm (see, e.g., Japanese Patent Application Laid-open No. 2002-111011 as Patent Document 1).
Such a vacuum pressure sensor which measures a pressure in a semiconductor chip manufacturing process or in any other vacuum equipment is provided with a vacuum chamber and having individual two sensors, i.e., an atmospheric pressure sensor which confirms that an atmospheric pressure is achieved in a vacuum chamber when inputting or removing a silicon wafer as a material or a semiconductor chip as a product and a vacuum pressure sensor which measures a pressure of a process gas which flows into the vacuum chamber in a process, e.g., CVD (Chemical Vapor Deposition) is almost close to a vacuum.
It is to be noted that such a vacuum pressure sensor is generally provided with a pressure-sensitive capacitance detecting portion in a region of a sensor diaphragm where sensitivity with respect to a pressure is large and a reference capacitance detecting portion in a region where sensitivity with respect to a pressure is small, and the reference capacitance detecting portion is used to just compensate an output drift of the pressure-sensitive capacitance detecting portion involved by a change in temperature around the pressure sensor.
Patent Document 1: Japanese Patent Application Laid-open No. 2002-111011